Not only is there such a thing, then, as unconscious thought, but it is probable that the best thinking is rarely, if ever, done under the influence of consciousness. The poet creates his work when the inspiration is on him and he is forgetful of himself and the world. Consciousness may aid in pruning and polishing, but in creating it often interferes with, rather than helps, the cerebral action. I think any one of my readers who has done any literary or scientific writing will agree that his or her best work is performed when self and surrounding objects have disappeared from thought and consciousness scarcely exists more than it does in a dream. Sometimes the individual is conscious of the flow of an undercurrent of mental action, although this does not rise to the level of distinct recognition. Oliver Wendell Holmes speaks of a business-man of Boston who, whilst considering a very important question, was conscious of an action going on in his brain so unusual and painful as to excite his apprehension that he was threatened with palsy; but after some hours his perplexity was all at once cleared up by the natural solution of the problem which was troubling him, worked out, as he believed, in the obscure and restless interval. "Jumping to a conclusion," a process to which the female sex is said to be especially prone, is often due to unconscious cerebration, the reasoning being so rapid that the consciousness cannot follow the successive steps. It is related that Lord Mansfield once gave the advice to a younger friend newly appointed to a colonial judgeship, "Never give reasons for your decisions. Your judgments will very probably be right, but your reasons will almost certainly be wrong." The brain of the young judge evidently worked unconsciously with accuracy, but was unable to trace the steps along which it really travelled.
We are not left to the unaided study of our mental processes for proof that the human brain is a mechanism. In the laboratory of Professor Goltz in Strasburg I saw a terrier from which he had removed, by repeated experiments, all the surface of the brain, thereby reducing the animal to a simple automaton. Looked at while lying in his stall, he seemed at first in no wise different from other dogs: he took food when offered to him, was fat, sleek and very quiet. When I approached him he took no notice of me, but when the assistant caught him by the tail he instantly became the embodiment of fury. He had not sufficient perceptive power to recognize the point of assault, so that his keeper, standing behind him, was not in danger. With flashing eyes and hair all erect the dog howled and barked furiously, incessantly snapping and biting, first on this side and then on that, tearing with his fore legs and in every way manifesting rage. When his tail was dropped by the attendant and his head touched, the storm at once subsided, the fury was turned into calm, and the animal, a few seconds before so rageful, was purring like a cat and stretching out its head for caresses. This curious process could be repeated indefinitely. Take hold of his tail, and instantly the storm broke out afresh: pat his head, and all was tenderness. It was possible to play at will with the passions of the animal by the slightest touches.